Redox Potentials and Denitrification in a Cropped Potato Processing Waste Water Disposal Field

Abstract

Abstract Many potato processors apply processing waste water containing nitrogen and other plant nutrients to cropped land. More than 1 metric ton of N per hectare was applied each year when waste water application averaged 230 cm/year on one field for 2 years. Less than 300 kg N/ha was recovered in the harvested grass hay, and only about 15 kg N/ha leached each season. Redox measurements made at several depths from 5 to 150 cm showed poorly aerated zones in the soil profile because of a high water table during the summer. Under these conditions, nitrate leached into these poorly aerated zones would be denitrified. Sufficient decomposable organic matter was present to provide energy for denitrification.